The Rena lies in two pieces after overnight bad weather pounded the vessel, on Jan. 8, 2012 in Tauranga, New Zealand.

The MV Rena cargo ship that ran aground off the coast of New Zealand in October has broken up in heavy seas, sparking fears of a new oil spill.

According to the New Zealand Herald, the Rena is lying in two pieces near Astrolabe Reef, off the North Island, where it crashed on Oct. 5. The Greek-owned vessel split apart after being pounded by waves of up to 6 meters (20 feet) on Saturday night, a spokesman for Maritime New Zealand (MNZ), Ross Henderson, told the BBC.

Oil has been seen leaking from the wreck, the Associated Press reported. According to Alex van Wijngaarden, on-scene commander for the national response team:

"While reports at this stage indicate there has not been a significant release of oil, with the Rena in its current fragile state, a further release is likely."

Authorities did not know how much oil had been leaked, van Wijngaarden said, but were "ready to respond" to whatever comes ashore.

About 385 tonnes of oil are believed to be still aboard the Rena. According to Environment Minister Nick Smith, any new spill now will be significantly less dangerous than the original leak:

"The risk to the environment is a fragment of what it was, with at the most tens of tonnes of oil rather than hundreds of tonnes that potentially could be spilled.

Most of the oil is reported to be in tanks in the Rena's stern section, which MNZ warns is listing heavily and looks likely to capsize. Some of the oil could end up dispersing in the ocean rather than washing up on beaches, the AP said.

Tonnes of milk powder that were among the Rena's cargo have already been spilled, surrounding the Rena with cloudy waters. Timber and other debris have also been spotted, the Herald reported.

Between 200 and 300 cargo containers had been washed overboard by this morning. Most are expected to sink. The main priority is to stop debris coming to shore, clean-up specialists said.

Modelling suggests that the Bay of Plenty coastline, particularly south-east of Mount Maunganui, is mostly likely to be affected. Maritime New Zealand has advised residents to stay out of the water and report any debris to authorities.

Hundreds of tonnes of oil and containers were spilt when the Rena first ran aground, killing more than 1,000 sea birds, covering hundreds of penguins in oil and necessitating months of clean-up. The incident has been described as New Zealand's worst-ever maritime disaster.

The ship's captain and other officers face criminal charges relating to the wreck, the BBC reported.